Spectrographic representations and waveforms showing the different types of NLP observed in infant African elephant roars. The roar in (a) starts with chaos, passes into harmonics around 0.5 s and subharmonics at F0 , F0 ,…, changes to chaos at 1.6 s, and grades into a rumble around 1.9 s. The roar is immediately followed by a low-frequency rumble. The roar in (b) starts with subharmonics at F0 ,…, passes into a harmonic segment at 0.5 s with a transition to a chaotic segment at 0.9 s, and grades into a rumble around 1.5 s. The roar in (c) is chaotic for the main part of the call, interrupted by a periodic (harmonic) window.
Estimated marginal means ± SE for the LMMs for (a) the HNR (log10 transformed) and (b) the call duration of the three behavioral contexts (S = suckling; P = protest; A = assistance). The significance levels of each pairwise comparison are given (*: p < 0.05, **: p < 0.001).
Definition of the behavioral indicators of arousal that occurred during vocalizations.
Definition of the broad behavioral categories in which roars occurred, the number of calls (N) that were allocated to each context, the accompanying observed indicators of arousal, and the number (N) of calls per indicator of arousal for each context.
The ID, the age (in months), and the sex of the recorded infant elephants, and the number of roars per individual and context. (a) Mean call duration (Mean call D, in s), mean F0 from harmonic segments (in Hz), the first three spectral peaks (Peak 1−3, in Hz), the mean HNR (in dB), and (b) total call duration (D total; in s), duration (in s) and percentage relative duration (%) of harmonics (Har), chaos (Chaos), and subharmonics (Sub) found in infant African elephant roars.
Confusion matrix showing the percentage of correct classification (given in bold) and misattribution for each subject (age is given in months). Correct reclassification after the leave-one-out, cross validation procedure is also given for each subject.
Results of discriminant function analysis for roaring vocalizations. Eigenvalues, variances explained, and structure matrix giving the correlation of variables.
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